# When candle wax is heated, it melts and becomes a liquid. When the liquid wax is then left to cool, it solidifies back into a solid. Explain, in terms of particles and energy, what happens during the melting of the candle wax, and state why melting is described as a physical change rather than a chemical change.

> Pearson Edexcel International GCSE Physics (4PH1) — 5.2 Change of state · Explain · 4 marks

> Candle wax melts at approximately 57 °C. When a candle is lit, the solid wax near the flame melts into a liquid. When the flame is blown out, the liquid wax cools and solidifies again.

## Mark scheme (4 marks)

1. During melting, energy supplied goes towards separating / freeing the particles from their fixed positions (rather than increasing kinetic energy / temperature)
2. The temperature remains constant / does not rise during melting because the energy is used to change state, not increase kinetic energy
3. Melting is a physical change because the process is reversible / the wax can return to its original solid state on cooling (freezing)
4. In a chemical change, the chemical structure of the substance changes and the original properties cannot be restored; this does not happen when wax melts

## Key terms

- [melting](https://www.gradenine.co.uk/glossary/melting)
- [physical change](https://www.gradenine.co.uk/glossary/physical-change)
- [chemical change](https://www.gradenine.co.uk/glossary/chemical-change)

## Related

- [Revision notes for Pearson Edexcel International GCSE Physics (4PH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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